The invention relates to an electronic device comprising a body including a substrate on which at least one electronic component is situated, which electronic component is connected to one or more connection areas and is sealed off from the environment by means of a cover on the component, which cover is provided on the substrate and forms a cavity above said component, said cover comprising a first body, which is situated on the substrate and which is provided, at the location of the component, with an opening, and said cover comprising a second body, which is situated on the first body and closes the opening. If the component comprises an acoustic wave filter, such a device is advantageously used in, inter alia, mobile telephones. The invention also includes a semiconductor device provided with such a device and a method of manufacturing such a device.
Such a device is disclosed in European patent 0.367.181, published on 20.04.1994. In said document, a description is given of an acoustic wave filter formed in and on a piezoelectric substrate of LiTaO3. Said filter is sealed off from the environment by a cover provided on the substrate, which cover forms a cavity above the filter. As a result, the filter is protected against dust and other influences from the environment, such as attenuation, so that an accurate and stable frequency selection is possible. Said cover comprises, for example, a synthetic resin cap or a ring onto which a metal plate is secured.
A drawback of the known device resides in that it is not very compact and cannot be readily integrated in a semiconductor device.
Therefore, it is an object of the invention to provide a device that is compact and that can be readily integrated in a semiconductor device and that is also easy to manufacture.
To achieve this, a device as described in the opening paragraph is characterized in accordance with the invention in that the first body comprises a lacquer layer, and the second body comprises a photoresist layer, and the lateral dimensions of the opening as well as the thickness and the material of the second photoresist layer are chosen to be such that the thickness of the cavity is above zero throughout the surface of the component.
The invention is first of all based on the recognition that the use of (photo)resist layers enables the thickness of the cover to be very small, so that the device in accordance with the invention can be very compact as a result of, in particular, a small thickness and hence can particularly suitably be integrated on a semiconductor device that is used, for example, in a mobile telephone. In addition, the invention is based on the surprising recognition that a suitable choice of the thickness and the material of a photoresist layer enables, at predetermined lateral dimensions of the cavity to be formed, this cavity to be formed in a thickness above zero throughout the surface area of the component. This is very important, in particular, in connection with an accurate and stable frequency selection of an acoustic filter. The use of a photoresist for the uppermost layer of the cover additionally has the important advantage that this layer can be readily provided with further openings, by means of photolithography, at the location of the connection areas of the component. For this purpose, also the lacquer layer is provided, at the same locations, with a further opening.
Consequently, in an important embodiment, also the lacquer layer comprises a photoresist, and further openings are situated in the lacquer layer and in the photoresist layer at the location of the connection areas of the electronic component, in which openings contact bumps are situated on the connection areas. As a result, the device can be very readily integrated, namely by means of a surface mounting technique, with a semiconductor device which comprises, for example, a high-frequency circuit. Preferably, the contact bumps comprise a solder and, in connection therewith, the photoresist layer, and preferably also the lacquer layer, is a solder-repellent layer.
In a preferred embodiment, the lacquer layer and the photoresist layer comprise a solid foil. It has been found that such a foil can most suitably be used to satisfy the necessary requirements of the invention. Besides, such a foil can readily satisfy the requirement that it should be solder-repellent.
Preferably, the electronic component comprises a surface acoustic wave filter. On the one hand, the invention enables an accurate, stable frequency selection of such a filter, on the other hand, a compact integration of such a filter is very important to many applications, such as mobile telephony.
Therefore, the invention also comprises a semiconductor device which includes a semiconductor body with a substrate, and which is provided with one or more semiconductor elements provided with an electronic device in accordance with the invention.
The invention further comprises a method of manufacturing an electronic device comprising a body including a substrate on which at least one electronic component is formed, which electronic component is provided with one or more connection areas and is sealed off from the environment by providing the component with a cover on the substrate, a cavity being formed above the component, and said cover being formed by providing a first body on the substrate and providing said body with an opening at the location of the component, and by providing a second body on the first body, resulting in the opening being closed, which method is characterized in accordance with the invention in that the first body is formed by applying a lacquer layer on the substrate, and the second body is formed by applying a photoresist layer on top thereof, and the lateral dimensions of the opening, and the material and the thickness of the photoresist layer are chosen to be such that the thickness of the cavity is above zero throughout the surface area of the component.
Preferably, also for the lacquer layer use is made of a photoresist, and further openings are formed in the lacquer layer and in the photoresist layer at the location of the connection areas of the electronic component, in which openings contact bumps, preferably containing a solder, are formed on the connection areas. For the lacquer layer and for the photoresist layer use is preferably made of a solid foil, which is preferably solder-repellent. If for the electronic component use is made of a surface acoustic wave filter, a method in accordance with the invention enables an attractive device in accordance with the invention to be obtained in a very simple manner.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.